Volatile and nonvolatile nitrosamines in beer.

The occurrence of N-nitroso compounds was investigated at different stages in the production of four different beer types and in 14 retail beer samples. Only two N-nitroso compounds, namely N-nitrosodimethylamine (0.17 +/- 0.18 microgram/kg; not detected to 0.60 microgram/kg) and N-nitrosoproline (1.51 +/- 1.01 micrograms/kg; range 0.5-3.60 micrograms/kg) were detected. For moderate beer drinkers, the N-nitrosodimethylamine exposure levels are unlikely to present a significant health risk while the presence of noncarcinogenic N-nitrosoproline does not pose any hazard to human health.